Mechanism for producing step-by-step linear drive



1956 H. D. GAIITE 2,772,32

MECHANISMS FOR PRODUCING STEP-BY-STEP LINEAR DRIVE Filed May 4, 1953 2 Sheets-Sheet 3!.

ATTORNEY W. 27, 1956 H. D. GAIITE. v 13 3 MECHANISMS FOR PRODUCING STEP-BYSTEP LINEAR DRIVE Filed May 4, 1953 2 Sheets-Sheet. 2

/N VEN T0 1? /Mvm ATTORNEY United States Patent M MECHANISMS FOR PRODUCING STEP-BY-STEP LINEAR DRIVE Harold D. Gaite, Taplow, England, assignor to British Telecommunications Research Limited, Taplow, England, a British company Application May 4, 1953, Serial No. 352,937

Claims priority, application Great Britain May 5, 1952 Claims. (Cl. 178-17) The present invention relates to mechanisms for producing a step-by-step linear drive and has particular ap plication to mechanisms for use in the telecommunication art though it is not limited thereto. It may for instance be used with advantage in tape readers as used in automatic transmission heads in teleprinter work. Various proposals have already been made for giving a drive of the type required and it is the chief object of the present invention to produce an improved arrangement which is simpler in construction and more reliable in operation.

According to the invention the so-called rectangular movement of the driving device which is required in the circumstances outlined is obtained by the use of two electromagnets, which may be of identical construction, arranged with their respective directions of operative motion at 90 so that in effect one magnet moves the driving member into and out of engagement with the tape while the other produces the necessary longitudinal movement for feed purposes. This arrangement produces a very simple and economical construction and can be mounted to occupy a comparatively small space.

The two magnets may be operated in sequence by time-displaced pulses from a source which may be common to a number of driving devices or the energisation of the magnets at the appropriate times may be effected by interrupter springs controlled by the magnets themselves. As a further alternative pulses may be fed to both magnets from the same supply but in one case through a delay arrangement, and for this purpose one of the magnets may be slugged or the delay may be obtained by an electrical network. If the delay is entirely independent of the magnet, it may be changed over from one magnet to the other by a simple switching operation which has the effect of reversing the drive and for some purposes this may be an added convenience.

The invention will be better understood from the following description of two alternative embodiments which show its application to a tape reader for teleprinter work and which are illustrated in the accompanying drawings in which:

Figs. 1-4 show a preferred form of device in each of its four different operative positions.

Figs. 5 and 6 illustrate diagrammatically alternative driving arrangements,

Figs. 7-ll illustrate an alternative form of constructron.

Fig. 12 illustrates diagrammatically a further driving arrangement not employing an external pulse source.

Referring first to Figs. 1-4, electromagnet 1 on the right serves to produce vertical movement of driving member 2, while electromagnet 3 on the left, which is similar, produces substantially horizontal movement of the driving member, that is to say the actual feed and return motions. Electromagnet 1 comprises an L- shaped heelpiece 4 to which is secured a core 5 carrying a coil 6. The magnet is provided with an armature 7 which is pivoted at 8 and is directly linked to the driving member 2,772,325 Patented Nov. 27, 1956 2 at the point 9. The armature is extended beyond the pivot 8 and a restoring spring 10 is attached to the extension and to a post 11 on the heelpiece. The electromagnet 3 similarly comprises a heelpiece 12, a core 13, a coil 14 and an armature 15 which. is pivoted to the heelpiece at 16 and is restored to normal by a spring 17 secured to a post 18 on the heelpiece 12. Pivoted to the end of this armature 15 at 19 is a connecting rod 20 which is pivoted to the driving member 2 at 21. The connecting rod extends beyond the pivot 21 and pivoted to its end at 22 is a link 23 which in turn is pivoted at 24 to a rocker arm 25. This arm is pivoted at 26 and at its opposite end is provided with a block 27 carrying the detent pins 23 and also a withdrawal bar 29 which serves to depress a set of peckers 30 clear of the tape 31. It will be appreciated that in the rest position shown in Fig. l the detent pins 28 engage with the driving perforations in the tape and thus prevent its movement.

In operation, the magnet 1 is first. energised and, as shown in Fig. 2, raises the driving member 2 so that pins 32 on its upper end engage in the driving perforations in the tape. The linkage ensures that when the driving member 2 moves upwards, the right-hand end of the connecting rod 20 also moves upwards and the rocker arm 25 is rotated counter-clockwise about its pivot 26 and consequently the detent pins 28 are moved downwards clear of the tape and at the same time the bar 29 withdraws the peckers from the tape if they are at this time engaging in any perforations therein,

Shortly thereafter electromagnet 34 is energised and causes the connecting rod 20 to be moved to the right so that the parts then occupy the positions shown in Fig. 3. N0 appreciable change is made in the position of the rocker arm 25 but the driving member 2 moves to the right and feeds the tape forward one step.

In the third stage as shown in Fig. 4, electromagnet 1 is de-energised so that the driving member 2 moves downwards withdrawing the pins 32 from the tape, while the rocker arm 25 is now rotated clockwise so that the detent pins 28 again engage the tape. Moreover the bar 29 enables the peckers to return to their normal position so as to sense the holes in the tape representing signals. Finally electromagnet 3 also is de-energised with the result that the driving member 2 is moved to the left but no change takes place in the position of the rocker arm 25 or the detent pins 28.

The cycle just described would be that normally employed and serves to drive the tape to the right. Ifhowever the magnets are pulses in reverse order the tape will be driven to the left and this is sometimes a convenience.

Possible driving arrangements are shown diagrammatically in Figs. 5 and 6. in Fig. 5 it is assumed that pulses are obtained at suitable intervals from the source P1 and, with the reversing switch R in the top position, are fed directly over lead 40 to electromagnet 1 and by way of the delay device D and over lead 41 to electromagnet 3. With suitable values for the pulse ratio and the delay produced by the device D, this will give operation in the manner described above. If it desired to produce reverse drive, the switch R is thrown to its bottom position Whereupon the connections are reversed.

Fig. 6 represents a somewhat similar arrangement except that the pulse source P2 is assumed to involve switching arrangements whereby two sets of pulses are produced over leads 42 and 43 with a definite phase relationship which may be adjustable. In this case also reversal of the drive may be effected by reversing the connections of the pulses by throwing the switch R.

Alternatively it may be arranged as shown in Fig. 12 that the circuit of magnet 1 is completed over break contacts controlled by magnet 3 while the circuit of magnet 3 is completed over make contacts controlled by magnet 1. A further control may be included in the circuit of magnet 1 as indicated at X. Suitable shunts and/or slugs may be provided if necessary to give a satisfactory speed of operation. This arrangement does not lend itself so readily to reversal of the drive but avoids the necessity for an external pulse source.

Adjustment and assembly of the mechanism is very simple and the two electromagnets may be identical but mounted with their axes at right angles. The transverse movement of the driving member is limited by back-stop 33 and front-stop 34, while vertical movement is limited in the forward position by the tail 35 of the rocker arm engaging the connecting rod 20 and in the normal position by back-stop 36. The whole mechanism is preferably assembled on a plate offset from the tape and all the components are then on one side of the plate and readily accessible for adjustment.

Figs. 7, 8, 9 and 10 show an alternative form of construction in which the majority of the parts are substantially identical with those of Figs. 1-4 and are identified by like reference numerals. In this modified form, how ever, the rocker arm 25 pivoted at 26, and carrying the block 2,7 with thedetent pins 28 is not directly linked to an extension of the connecting rod but is, instead, provided with a ramped surface 38 on its underside for co-operative engagement with a detent or bent 39 which is adjustably secured to a laterally projecting extension arm 40 on the driving member 2. The rocker arm is urged to rotate about its pivot 26 by spring means, not shown. The front stop 34 for limiting the horizontal movement of the driving member 2 is now arranged to engage the end of such extension arm 40 instead of the connecting rod 20.

In the operation of this modified device the magnet 1 is first energised and raises the driving member 2 so that the pins 28 engage in the holes in the tape 31 as in the previous embodiment while at the same time the bent 39 engages the surface 38 of the rocker arm 25 to rotate it in an anticlockwise direction and thus causes removal of the detent pins 28 from the tape while at the same time depressing the peckers as shown in fragmentary form in Fig. 8. When, at the second stage, the electromagnet 3 is energised, theconnecting rod 20 is moved to the right thusrnoving the driving memberZ to the right andfeeding thetape forward one step as shown in Fig. 9. The bent 39/continues to engage the surface 38 of the rocker arm 25 whereby thedetent pins 28 are held depressed together with the peckers 30.

In the third stage of movement as shown in Fig. 10

electromagnet 1 is de-energised so that the driving member 2 moves downwardly to withdraw the pins 32 from the tape while the lowering of the bent 39 allows the rocker arm 25 to rotate clockwise and thereby to lift the detent pins 28 so that these again engage the tape 31. The I raising of the bar 29 simultaneously allows the peckers 30 to return to their normal position to sense the holes in the tape. Finally electromagnet 3 is deenergized whereby the mechanism returns to the position shown in Fig. 7.

This modified construction is also reversible but Where reversibility is not required a slightly modified form of operationmay be obtained by adjusting the position of the bent 39 slightly more to the right as shown in Fig. 11 whereby, at the end of the second stage of operation the surface 38 on the rocker arm 25 drops off the left hand end of the bent 39 thereby allowing the immediate return of the detent pins 28 to engage the perforations in the tape accompanied by the simultaneous return of the peckers 30 to their normal hole sensing position.

I claim:

1. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a rectangular movement, comprising a first electromagnet, a first spring, means effective on the energisation of said first electromagnet for moving said drive member in the direction of its length against the tension of said first spring, a second electromagnet, a second spring, means effective on the operation of said second electromagnet for moving the operative end of said drive member substantially at right angles to its length against the tension of said second spring, and means for repeatedly energising both said electromagnets at the same frequency and for the same periods but with a predetermined time displacement such that the periods of energisation overlap.

2. A stcp-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a rectangular movement, comprising a first electro magnet, a first spring, means effective on the operation of said first electromagnet for moving said drive member in the direction of its length against the tension of said first spring, a second electromagnet, a second spring, means effective on the operation of said second electromagnet for moving the operative end of said drive member at right angles to its length against the tension of said second spring, a source of pulses and connections from said source to said magnets whereby pulses from said source cause the repeated energisation of said electromagnets at the same frequency but with a predetermined time displacement such that the pulses overlap.

3. A step-by-step linear drive mechanism as claimed in claim 2 in which the pulses from said source are applied to said first and second electromagnets simultaneously and said second electromagnet is provided with a slug to cause it to operate with a predetermined time delay after the operation of said first electromagnet.

4. A step-by-step linear drive mechanism as claimed in claim 2 in which pulses from said source are fed directly to said first electromagnet and are fed to said second electromagnet by way of a delay network so that said electromagnets operate with a predetermined time dis placement in response to the same pulse from said source.

5. A step-by-step linear .drive mechanism as claimed in claim 4 including a reversing switch connected between said electromagnets and said pulse source and said delay network respectively, whereby in response to the operation of said reversing switch the movement of the operative end of said elongated drive member may be caused to take place in theopposite direction.

6. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a rectangular movement, comprising a first electromagnet, a first spring, means effective on the opperation of said first electromagnet for moving said drive member in the direction of itsv length against the tension of said first spring, a second electromagnet, a second spring, means effective on the operation of said second electromagnet for moving the operative end of said drive member at right angles-to its length against the tension of said second spring, a first source of pulses, a second source of pulses supplying identical pulses at the same frequency as said first source but with a predetermined time displacement such that the pulses from the two sources overlap, connections from said first pulse source to said first electromagnet and connections from said second pulse source to said second electromagnet.

7. A step-by-step linear .drive mechanism for causing the operative end of an elongated drive member to perform a rectangular movement, comprising a first electromagnet, a first spring, means effective on the operation of said first electromagnet for moving said drive member in the direction of its length against the tension to said second electromagnet including said make contacts whereby said electromagnets are repeatedly energized in succession.

8. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a rectangular movement to effect the feed of a tape, comprising a first electromagnet, a first spring, means effective on the operation of said first electromagnet for moving said drive member in the direction of its length against the tension of said first spring, a second electromagnet, a second spring, means effective on the operation of said second electromagnet for moving the operative end of said drive member at right angles to its length against the tension of said second spring, a holding member for retaining said tape in position between the feeding strokes of said drive member and mounted so as to be movable in substantially the direction of the length of said drive member, a linking member between said holding member and said drive member such that when said drive member is moved in the direction of its length said holding member is moved in the opposite direction, a source of pulses and means for feeding pulses from said source to said electromagnets respectively With a predetermined time displacement such that the pulses overlap.

9. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a rectangular movement, comprising a first electromagnet, means effective on the energization of said first electromagnet for moving said drive member in the direction of its length, means for reversing said movement on the de-energisation of said first electromagnet, a sec ond electromagnet, means effective on the energisation of said second electromagnet for moving the operative end of said drive member substantially at right angles to its length While maintaining the non-operative end substantially fixed, means for reversing said right-angle movement on the de-energisation of said second electromagnet and means for energising said first and second electromagnets in turn and subsequently de-energising them in turn.

10. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a rectangular movement, comprising a first electromagnet, an armature for said first electromagnet connected to the non-operative end of said drive member and arranged to move said drive member in the direction of its length on the energisation of said first electromagnet, a restoring spring for said armature, a second electromagnet, an armature for said second electromagnet, a link connected to said second electromagnet armature and to said drive member near its operative end so as to be substantially at right angles to said drive member, said second electromagnet armature being arranged to move said link in the direction of its length on the energisation of said second electromagnet, a restoring spring for said second electromagnet armature, and means for energising said first and second electromagnets in turn and subsequently tie-energising them in turn.

References Cited in the file of this patent UNITED STATES PATENTS 2,172,269 Angel et a1. Sept. 5, 1939 2,262,012 Lake Nov. 11, 1941 2,263,721 Lorme Nov. 25, 1941 2,278,196 Fluharty Mar. 31, 1942 2,586,669 Lake Feb. 19, 1952 

